Measuring the spectral directional hemispherical reflectance of a sample remains a complex task. Such a process may involve placing a reference material having a known level of reflectance in a measuring device, measuring reflectance values of the reference material, removing the reference material from the device, determining a correction value based on the measured values for the reference material, replacing the reference material with a sample to be measured, and then finally measuring the sample.
These issues are compounded when attempting to accurately measure reflectance of a sample at high angles of incidence (i.e., angles that are close to tangential/parallel with the surface) at a high degree of accuracy. Some devices attempt to account for this issue by utilizing an interior surface of the measuring device as a reference material. However, such devices are capable of only single angle measurements, which substantially increases the amount of labor involved in quantifying the reflectance of a sample at a variety of angles of incidence.
Because of the issues described above, designers of devices that measure spectral hemispherical reflectance continue to seek out enhanced designs that are capable of rapidly measuring reflectance across a variety of angles of incidence, and that also are capable of accounting for potential sources of error when taking such measurements.
Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.